1. Field of the Invention
The present invention relates to a contact mask having guard ring patterns used for manufacturing a semiconductor device and, more particularly to a contact mask having guard ring patterns which can prevent a lifting of a photoresist film in guard ring regions.
2. Brief Description of the Prior Arts
Generally, in a manufacturing process of the semiconductor device, a connection between the junction and the conductive layer or between the conductive layers is accomplished by a contact hole formed in an insulating layer. Also, when the contact hole is formed, a guard ring is formed on the insulating layer along an edge of a die. The guard ring is formed to prevent defects due to an electrical influence between neighboring dies upon a wafer level test. A conventional contact mask used for forming a contact hole and a guard ring will be explained below by reference to FIG. 1.
FIG. 1 is a partial plan view of a conventional contact mask. In a contact mask 9, a transparent substrate 1 is made of materials such as quartz. A plurality of contact patterns 4 are formed on the substrate 1. A first guard ring pattern 2 and a second guard ring pattern 3 are located along the around portion of the contact patterns 4, respectively. Each of the first and second guard ring patterns 2 and 3 has a continuous pattern with a line shape. The second guard ring pattern 3 is located at an inside of the first guard ring pattern 2.
The process for forming a contact hole and a guard ring using the contact mask having a structure described above will be explained by reference to FIGS. 2 and 3.
FIG. 2 is a partial plan view of one of the dies for explaining the state in which a lithography process is implemented using the contact mask 9 shown in FIG. 1, and FIG. 3 is a cross-sectional view taken along line 3--3 of FIG. 2. A photoresist film 5 is formed on an insulating layer 7 formed on a silicon substrate 8, the photoresist film 5 is then patterned through the exposure and development process using the contact mask 9 as shown in FIG. 1. The insulating layer 7 is wet etched at a given depth and the remaining insulating layer 7 is then dry etched using the patterned photoresist film 5 as a mask to form a plurality of contact holes 6 in the insulating layer 7. Meanwhile, during etching processes, the outside portion of the insulating layer 7 corresponding to the first and second guard ring patterns 2 and 3 of the contact mask 9 is etched, thus a first guard ring g1 and a second guard ring g2 are formed.
In manufacture of a highly integrated device, since a BPSG film containing a large amount of impurity ions is used as the insulating layer 7 to improve the flatness of the surface, the etching rate of the insulating layer 7 made of BPSG is increased in a wet etching. Due to characteristics of wet etching, the insulating layer 7 is laterally overetched, and the photoresist film 5, which is formed on the insulating layer 7 between the first guard ring g1 and the second guard ring g2 after a wet etching process, is lifted. The lifted photoresist film 5 is buried into an adjacent contact hole 6, therefore, the contact holes having a complete structure can not be formed through a following dry etching process so that the device is defective. As a result, yield of the device is lowered.